Various types of pumps exist for the purpose of pumping fluids, such as liquids. Many flow cytometers use peristaltic pumps, which have many advantages. Peristaltic pumps are positive displacement pumps. The fluid being pumped only contacts the flexible tubing and is not exposed to other pump components which could possibly cause contamination of the fluid being pumped. Both highly sterile fluids, as well as chemicals, can be pumped through a peristaltic pump since the fluids only contact the flexible tubing. Peristaltic pumps are especially suited for pumping abrasives, viscous fluids, and biological fluids.